Differences in performance between right and left hands during visually guided reaching, bimanual and unimanual object manipulation, and rhythmical tapping will be assessed longitudinally for 20 infants from 9 to 18 months of age. The infants' performance will be recorded on videotape at 40, 50, 60, and 75 weeks of age and manual specialization will be described. The development of manual specialization will be compared among the different domains of manual performance and with the manual specialization these infants exhibited during their first 8 months of life. The data will also assess the influence of head orientation performances on the development of handedness. The data also provide a means for observation of hemispheric specialization of function during the period when infants begin their acquisition of speech.